1. Field of the Invention
This invention relates to the monitoring of the integrity of a cable designed for supporting a load underwater.
The invention is particularly but not exclusively applicable to the monitoring of a cable which carries at its lower end a sonar body and which trails from the stern of a vessel for towing the sonar body at a predetermined depth beneath the surface of a body of water.
2. Description of the Prior Art
Among the problems encountered in such a system is the development of microcracks in or complete failure, i.e. breakage, of one or more of the load bearing wires making up the cable. This problem may be the result of overloading due to operator error, equipment malfunction, or adverse sea conditions or the like, or may be the result of metal fatigue. Almost invariably the development of microcracks or failure of a wire takes place at or near the point at which the cable is joined or terminated to the sonar body. It has previously been proposed to monitor the occurrence of cracks or breakages in a variable depth sonar system by monitoring the acoustic emissions which arise from the cable upon occurrence of a crack in or failure of a wire.